Physics Review Question Unit: Optics Year: 1993 Question#: 92 Question: The diagram below represents a convex (converging) lens with focal point F. If an object is placed at 2F, the image will be (1 ) virtual, erect, and smaller than the object (2 ) real, inverted, and the same size as the object (3 ) real, inverted, and larger than the object (4 ) virtual, erect, and the same size as the object What is this question really asking? Explanation by: David V [ Return to question menu ] Answer 1 virtual, erect, and smaller than the object INCORRECT When an object is placed outside of the focal length of a converging lens, the image is real, not virtual. Also, an object placed outside the focal length of a converging lens creates an inverted image (see diagram.) return to top Answer 2 real, inverted, and the same size as the object CORRECT See diagram. The image is real because the object is placed outside the focal length of a converging lens. Using congruent triangles, we see that AB = CD, thus the image is also the same size as the object. return to top Answer 3 real, inverted, and larger than the object. INCORRECT See diagram. The object is real and inverted, but we can see through congruent triangles that AB= CD, which means that the image is the same size as the object. return to top Answer 4 virtual, erect, and the same size as the object. INCORRECT return to top |